Solar energy apparatus

ABSTRACT

Described herein are solar energy apparatus that overcome many of the disadvantages and shortcomings of conventional solar energy absorption structures. The solar energy apparatus may comprise inexpensive material and have smaller dimensions to reduce the overall cost of the apparatus. The apparatus may also have coatings which help to maximize the amount of solar energy absorbed and minimize the deterioration of the apparatus due to overheating. The apparatus may include a system for monitoring and controlling the temperature of the apparatus to prevent overheating.

This application claims the benefit of priority to U.S. ProvisionalApplication No. 60/901,063, filed Feb. 12, 2007, the entirety of whichis incorporated by reference.

BACKGROUND

Solar energy absorption structures or panels for absorbing solar energyare known in the art. Such conventional solar energy absorptionstructures typically include a body or frame and an energy absorptionfluid flowing through the body. Many of these conventional solar energyabsorption structures have various shortcomings.

For example, conventional solar energy absorption structures aretypically made of materials—such as optical glass, aluminum, orcopper—which can result in structures that are often difficult toinstall, heavy and costly to manufacture.

Further, many of the components of conventional solar panels have solidblack absorbing surfaces that can often overheat, thereby resulting inextreme stress on the solar panels. More specifically, when exposed tothe sun, a conventional solar panel can heat up to between 300° F. and400° F. if energy absorption fluid has been drained from the panel, orif energy absorption fluid is not being continuously pumped through thepanel, e.g., during fluid stagnation periods. In order to prevent damageto or extreme stress on the panels, conventional solar panels must bemade of materials that are able to resist such high temperatures. Suchmaterials are typically expensive.

Another known shortcoming of conventional solar energy absorptionstructures is that energy absorption fluid has a propensity to overheatwhen exposed to sunlight during fluid stagnation periods. Also, in someclimates, such as Northern climates, antifreeze is added to the energyabsorption fluid to prevent damage. However, during fluid stagnationperiods, the antifreeze can be heated to levels that can ruin or degradethe antifreeze. In the event the antifreeze becomes degraded, the fluidcan become acidic and dissolve the components of the absorber and otherparts of the system and piping, thereby requiring maintenance. Moreover,damage to a fluid can be difficult to detect unless checked by aprofessional. Accordingly, if the fluid is not checked regularly, justone instance of the fluid overheating can permanently damage the system.

Another known shortcoming of conventional solar energy absorptionstructures is that many such structures cannot produce uniform heattransfer at low cost.

SUMMARY

Described herein are various embodiments of solar energy apparatus thatovercome many of the disadvantages and shortcomings of conventionalsolar energy absorption structures.

In certain embodiments of the invention described herein, solar energyabsorbers that may comprise transparent plastic material are disclosed.The dimensions of the solar energy absorbers may be minimized so as toreduce the amount of energy absorption fluid, such as black fluid,flowing through the solar energy absorber. Reflective coatings,selective coatings for improved absorption and reflectors may also beincluded in the solar energy absorbers.

In other embodiments of the invention described herein, headers forsolar energy absorbers that may comprise transparent plastic materialsand reflective coatings are disclosed.

In other embodiments of the invention described herein, housings forabsorbers that may comprise foam or transparent plastic materials aredisclosed. The housings may also include reflective coatings. Thehousings may also include elements for holding an absorber in position.

In still other embodiments of the invention described herein, combinedabsorber and absorber housings are disclosed. The combined absorber andabsorber housings may comprise transparent plastic material or foam.

In yet another embodiment of the invention described herein, a solarabsorptive fluid circulation system is disclosed. The solar absorptivefluid circulation system may include a monitoring system for monitoringthe temperature of the system and valves that may be opened to drain thesystem of black fluid should the system exceed a predeterminedtemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are shown in the accompanyingdrawings.

FIG. 1 is a perspective view of an absorber of a solar energy apparatus.

FIG. 2 is a perspective view of an absorber of a solar energy apparatus.

FIG. 3 is a bottom end view of an absorber of a solar energy apparatus.

FIG. 3A is a bottom end view of an absorber according to one embodiment.

FIG. 3B is a bottom end view of an absorber according to anotherembodiment.

FIG. 3C is a bottom end view of an absorber according to yet anotherembodiment.

FIG. 4 is an end view of a center conductor of a solar energy apparatusaccording to one embodiment.

FIG. 5 is an end view of the center conductor illustrated in FIG. 4 butshown with energy absorption fluid flowing there through.

FIG. 6 is a side view blowup of a section of an absorber portion of theof a coaxial solar energy apparatus.

FIG. 7 is an end view blowup of a section of an absorber portion of theof a coaxial solar energy apparatus.

FIG. 8 is an end view blowup of possible center conductor configurationsin an absorber portion of a coaxial solar energy apparatus.

FIG. 9 is an end view of possible reflector shapes in an absorberportion of a coaxial solar energy apparatus.

FIG. 10 is the side view of an absorber portion of a coaxial solarenergy apparatus.

FIG. 11 is a blowup of the side view of the absorber portion of thecoaxial solar energy apparatus.

FIG. 12 is a three dimensional view of a coaxial solar energy apparatus.

FIG. 13 is a side view of a coaxial solar energy apparatus with headersattached.

FIG. 14 is a partial side view of a absorber of a solar energy apparatusshown with a header.

FIG. 16 is a cross-sectional end view of a solar energy apparatus.

FIG. 17 is a detailed view of the area inside the circle labeled Detail17-17 in FIG. 16.

FIG. 18 is an exploded perspective view of a solar energy apparatusaccording to one embodiment.

FIG. 19 is an end view of the solar energy apparatus of FIG. 18 shownwith an end cap removed.

FIG. 20 is a partial end view of the solar energy apparatus of FIG. 18shown with the end cap and a header removed.

FIG. 21 is a 3D view of an absorber assembly.

FIG. 21A is an end view of an absorber portion of a solar energyapparatus.

FIG. 22 is an end view of the shell portion of a solar energy apparatus.

FIG. 23 is an end view blow up of a solar energy apparatus.

FIG. 24 is an end view of a solar energy apparatus with end capsremoved.

FIG. 25 is a 3D view of the track and flexible beam.

FIG. 26 is a top view of a solar energy apparatus.

FIG. 27 is a side view of a solar energy apparatus.

FIG. 28 is a three dimensional view of a solar energy apparatus.

FIG. 29 is a perspective view of a solar energy apparatus having a topto bottom fluid flow according to one embodiment.

FIG. 30 is a top view of the solar energy apparatus of FIG. 29.

FIG. 31 is an end view of the solar energy apparatus of FIG. 29 shownwith an end wall removed.

FIG. 32 is a cross-sectional side view (without headers) of the solarenergy apparatus as shown in FIG. 33 taken along the line 32-32 in FIG.33.

FIG. 33 is a perspective view of the solar energy apparatus of FIG. 29shown with energy absorption fluid in the absorber.

FIG. 34 is an end view of an embodiment of a solar energy apparatushaving a plurality of vacuum chambers.

FIG. 35 is an exploded perspective view and an assembled perspectiveview of a modular solar energy apparatus according to one embodiment.

FIG. 36 is an exploded side view and an assembled side view of themodular solar energy apparatus of FIG. 34.

FIG. 37 is an exploded end view and an assembled end view of the modularsolar energy apparatus of FIG. 34.

FIG. 38 is a top plan view of the modular solar energy apparatus of FIG.34.

FIG. 39 is a perspective view of a plurality of modular solar energyapparatus coupled together.

FIG. 40 is a perspective view of a solar energy apparatus according toone embodiment.

DETAILED DESCRIPTION

Described herein are embodiments of solar energy apparatus forcollecting and distributing solar energy. The solar energy apparatusinclude a solar collector system through which a solar absorptive heattransfer fluid, such as black fluid, is allowed to flow. The solarenergy collector system may include a solar energy collection portionand a solar energy transfer portion. As the solar absorption fluid flowsthrough the solar energy collection portion, it contacts sun light andcollects solar energy. The solar absorption fluid then flows through thesolar energy transfer portion where the solar energy collected in thesolar absorption fluid is utilized immediately or is transferred to athermal energy storage system, such as a water heating or buildingheating system, via a thermal exchange element or a heat collectionstorage container. Continuing from the thermal energy transfer portion,the absorptive fluid returns to and again flows through the solar energycollection portion to restart the solar energy collection anddistribution process in a closed loop. Accordingly, the solar energyapparatus provides continuous collection and distribution of solarenergy.

With reference to FIG. 1, an absorber 20 for collecting solar energy isillustrated. The absorber 20 includes a generally rectangular shapedfront panel 22 spaced apart from and extending parallel to acorresponding generally rectangular shaped rear panel 24. The frontpanel 22 and rear panel 24 are coupled to each other along theirrespective sides 26, 28 by edge members 30. In a specific embodiment ofthe absorber, a light reflective layer 44 may be formed under the rearpanel 24. The absorber 20 has an overall length A.

The absorber 20 also includes a bottom header 60 at the bottom end 38 ofthe absorber 20 having an open end 70 and a closed end 72 and a topheader 62 at the top end 42 of the absorber 20 having an open end 70 anda closed end 72. Closed ends 72 may be open if there are a plurality ofabsorbers 20 placed in series or in parallel so that fluid may flowbetween absorbers. Also, the closed end 72 of the top header 62 and theclosed end 72 of the bottom header 60 do not need to be on the same sideof the absorber. The closed ends 72 may be on opposite sides of theabsorber so that flow goes in one side of the bottom header 60 and outthe opposite side of the top header 62, which creates more uniform fluidflow.

The bottom header 60 and top header 62 are in fluid communication withthe space between the front panel 22 and rear panel 24. The bottomheader 60 may include a fluid valve 113 and the top header may includean air valve 115.

In operation, energy absorptive fluid, such as black fluid, is flowedinto the open end 70 of the bottom header 60. The bottom header 60 fillswith energy absorptive fluid and eventually begins to fill the spacebetween the front panel 22 and the rear panel 24. Once the fluid hasreached the top end 42 of the absorber 20, the fluid flows into the topheader 62 and out the opening 70.

As shown in FIG. 2, solar absorptive heat transfer fluid 160 fills theabsorber 20 when solar absorptive heat transfer fluid 160 flows intobottom header 60 and up the absorber 20 to the top header 62

With reference to FIG. 3, the structure of the absorber 20 isillustrated in greater detail. The front panels 22 and rear panel 24 arecoupled to each other along their respective sides 26, 28 by edgemembers 30 and along respective inward surfaces by a plurality ofinternal members 32. Although not necessary, as shown in the illustratedembodiments, the edge members 30 and internal members 32 extendgenerally parallel to each other and the respective sides 26, 28 of thefront panel and rear panel 24. The edge members 30 are coupled, e.g.,adhered, to the sides 26, 28 of the front panel 22 and rear panel 24,and serve to seal the sides together. The internal members 32 arecoupled to the inward surfaces of the front panel 22 and rear panel 24to at least partially form a seal between respective internal membersand the inward surfaces of the front panel 22 and rear panel 24 and tokeep the front panels 22 and rear panel 24 from moving apart ortogether, such as when fluid between the panels is under pressure orsuction relative to outside air. In certain implementations, theinternal members 32 are coupled to the inward surfaces of the panels 22,24 through use of any of various bonding techniques, such as, but notlimited to, use of an adhesive.

The absorber 20 includes a plurality of fluid chambers 34 in which aheat exchange medium, such as solar absorptive heat transfer fluid, iscontained, absorbs sunlight, and is circulated. The fluid chambers 34include the areas defined between the inward surfaces of the front andrear panels 22, 24 and either adjacent internal members 32 or aninternal member 32 and an inward surface of an edge member 30. The fluidchambers 34 each have an inlet opening 36 proximate the bottom end 38shown in FIG. 1. The fluid chambers 34 also have an outlet opening (notshown) proximate the top end 42 of the absorber 20 shown in FIG. 1. Thefluid chambers 34 extend generally parallel to the sides 26, 28 of thepanels 22, 24 and generally perpendicular to the bottom and top ends 38,42 shown in FIG. 1.

The absorber 20 has an overall width B and overall depth C. The frontpanel 22 and rear panel 24 are spaced apart from each other a distanceE, i.e., the fluid chambers 34 have a depth or height E. The edgemembers 30 can have the same general length A (see FIG. 1) and depth C,respectively, of the absorber 20 and a width F. A first of the internalmembers 32 can be spaced a distance G away from an outer side of an edgemember 30 and a second of the internal members 32, i.e., the nextadjacent internal member, can be spaced a distance H, or “2 times G”,away from the outer side of the same edge member 30. In other words,each internal member 30 can be spaced a distance “n times H” away froman outer side of an edge member, where n is the number of internalmembers between the internal member in question (including itself) andthe edge member 30. In other embodiments, the internal members 30 can bespaced at any of various distances away from the outer side of the edgemembers 30 and relative to each other to form fluid chambers 34 havingany of various widths S. In other words, each chamber can have a width Sequal to the difference between the distance G and the width F of theedge members.

The front panel 22 and rear panel 24 are each made from a clearmaterial, such as optically transparent plastic, which permits energyemitted from the sun to pass through and heat the heat exchange medium.The plastic may have any or all of the characteristics of plastic as setforth in Table 1 below.

The rear panel 24 includes a light reflective layer 44 positionedadjacent an outer surface of the rear panel. For example, in someimplementations, the light reflective layer 44 is a metallic layer, suchas a thin piece of sheet metal, or foil, coupled to, such as by beingadhered to, or otherwise bonded to, the outer surface of the rear panel24. In some implementations, the reflective surface is spaced apart fromthe outer surface of the rear panel 24 such that an insulating layer ofair can be positioned between the reflective surface and the rear panel.

In one specific exemplary implementation, the overall length A isapproximately 96 inches, the overall width B is approximately 48 inchesand the overall depth C is approximately 0.13 inches. The thickness D ofthe front panels 22 and rear panel 24 is approximately 0.02 inches andthe panels are spaced apart a distance E of approximately 0.09 inches.The distance G is approximately 0.5 inches and the distance H isapproximately 1.0 inches. In this and other implementations, the weightof the absorber plus absorptive fluid is less than 30 pounds.

In some implementations, the components of the absorber can be madeusing plastic extrusion processes. For example, one or more of the frontand rear panels can be a polycarbonate panel, such as manufactured byGallina USA, of Janesville, Wis.

FIG. 3A depicts an alternative exemplary implementation of an absorber20A similar to absorber 20, but with a different overall depth C andchamber width S. The absorber 20A has an overall depth C ofapproximately 0.25 inches and a width S of the chambers of approximately0.25 inches. The absorber 20A can hold approximately 5 gallons ofabsorptive fluid.

Referring to FIG. 3B, in another specific exemplary implementation of anabsorber 20B that is similar to absorber 20 and formed using a plasticextrusion process, the overall length A is approximately 96 inches, theoverall width B is approximately 48 inches and the overall depth C isapproximately 0.16 inches. The thickness D of the front panel 22 andrear panel 24 is approximately 0.01 inches and the panels are spacedapart a distance E of approximately 0.14 inches. The width S of eachchamber is approximately 0.16 inches. The absorber of this specificimplementation can hold approximately 3 gallons of absorptive fluid,e.g., black fluid, and weigh less than approximately 35 pounds excludingthe black fluid.

In FIG. 3C, yet another exemplary implementation of an absorber 20C thatis similar to absorber 20 and formed using a plastic extrusion processis illustrated. The overall length A is approximately 96 inches, theoverall width B is approximately 48 inches and the overall depth C isapproximately 0.06 inches. The thickness D of each of the panels 22, 24is approximately 0.01 inches and the panels are spaced apart a distanceE of approximately 0.04 inches. The width S is approximately 0.25inches. The absorber 20C can hold approximately 1 gallon of solarabsorptive heat transfer fluid and weigh less than approximately 18pounds without fluid.

In addition to fluid chambers formed between two plates to form a solarenergy absorber as described above, the solar energy absorber may haveother configurations. Referring to FIGS. 4 and 5, and according toanother embodiment, a solar energy collector 300 includes a centerconductor collection portion 310. The center conductor 310 includes agenerally cylindrical inner conduit 320 and a generally cylindricalouter conduit 330 coaxial with and surrounding the inner conduit. Aninner surface of the inner conduit 320 defines an axially extendingfluid passageway 322 having a generally circular cross-section and theinner surface of the outer conduit 330 defines an axially extendingpassageway 332 having a generally circular cross-section with a radiusgreater than that of the fluid passageway 322. The outer conduit 330 canhave a maximum diameter L that in some implementations is approximately1.0 inches.

The outer conduit 330 is coupled to the inner conduit 320 by posts 324circumferentially spaced about and secured to an external surface of theinner conduit and an internal surface of the outer conduit. In someimplementations, the posts 324 are elongate and extend a length of thecenter conductor 310. In other implementations, the posts 324 arediscrete spacers, such as columns or blocks, positioned at incrementallocations along the length of the center conductor 310. Although threeposts 324 are shown in the illustrated embodiments, in otherembodiments, more or less than three posts are used.

In an alternative implementation, the posts 324 can be disks having acentral hole with a diameter that is approximately equal to the outerdiameter of the inner conduit and an outer diameter that isapproximately equal to the inner diameter of the outer conduit such thatthe disks rest between the inner and outer conduits and maintain theinner and outer conduits in coaxial alignment.

In one embodiment, the ratio of the length of each post 324 divided bythe cross-sectional area of each post 324 is maximized in order tominimize heat lost through conduction as heat moves axially up theposts.

The center conductor collection portion 310 includes a region 350defined between the inner and outer conduits 320, 330 within which avacuum is created to reduce convective heat losses. In someimplementations, an infrared reflective coating may be applied to theinterior surface of the outer conduit 330 to increase infraredreflection back into the fluid passageway 322 when visible and UV lightis converted into heat inside fluid passageway 322. With specificreference to FIG. 4, with no fluid present in the fluid passageway 322,the conductor 310 does not absorb solar energy as sunlight is allowed topass through the conductor and scatter.

In some embodiments, a portion of the lower half of any of the surfacesmay be coated with a light-reflecting surface so that light reflectsback to sky rather than passing through center conductor 310 when heatabsorptive fluid is absent. In certain implementations, one or more ofthe components of the center conductor 310 can be made of plastic,glass, plastic coated glass, or any combination thereof.

Referring to FIG. 5, in operation, solar absorptive heat transfer fluid360 is introduced in and allowed to flow within the fluid passageway 322by operation of a pump (not shown). With solar absorptive heat transferfluid 360 present and circulating through the center conductor 310,solar energy is collected by the solar absorptive heat transfer fluid360 as thermal energy and transferred to a thermal storage mass (similarto thermal storage mass 152 in FIG. 40 described in greater detailbelow) external to the center conductor 310.

In some embodiments, the collector 300 may be drained of fluid to reducethe overall temperature of the collection portion 310 in the event theoverall temperature exceeds a predetermined threshold. For example, inone specific implementation, the system drawing heat from the collector300 is a steam system and the thermal mass is a block of inexpensivemetal. The solar absorptive heat transfer fluid can be a hightemperature oil compound with T_(tm) _(—) _(max) set to 600° F. toprovide sufficient heat for generating steam and T_(c) _(—) _(max) setto just above 600° F. When the overall temperature T_(c) of thecollection portion 310 reaches T_(c) _(—) _(max), the pump turns off andthe fluid is allowed to drain from the center conductor 310. With nofluid being located within the conductor 310, the collector is placed inthe non-operative state and solar energy penetrating the conductor willpass through unabsorbed.

Because the overall temperature of the collector 300 can be controlled,expensive high-temperature glass or plastics need not be used, and lessexpensive glass and plastic substitutes can be used.

The inner conduit, outer conduit and posts may each be made of opticallytransparent plastic material. The plastic material may be, for example,polycarbonate plastic. The plastic may have any or all of thecharacteristics set forth in Table 1 below.

According to another embodiment, FIGS. 6 and 7 illustrate a side viewand a cross-sectional view of an absorber assembly 801. The absorberassembly 801 generally comprises an insulating tube 810, at least onespacer 820, a center conduit 830 and a reflector 840. The insulatingtube 810 and center conduit have a generally coaxial arrangement,wherein the spacer 820 centers the center conduit 830 within theinsulating tube 810 and maintains a space between the center conduit 830and the insulating tube 810. The spacer 820 also matingly receivesreflector elements 840 between each spacer 820. The reflector 840 isgenerally positioned in the insulating tube 810 below the center conduit830.

When in operation, solar absorptive heat transfer fluid flows throughthe center conduit 830 as described in greater detail below. Dependingon the level of desired insulation within the assembly, the sealed spacebetween center conductor 830 and insulating tube 810 may contain air, anoble or inert gas such as argon, or a vacuum.

The insulating tube 810 and the center conductor 830 run the full lengthof the absorber 801. In one embodiment, the diameter of the insulatingtube 810, I_d, equals twice the diameter, C_d, of the center conductor830. Incident solar energy enters the center conductor 830 directly orreflects off reflector 840 to enter the center conductor 830. Theplacement of the reflector 840 directly below the center conductor 830and with walls extending from the base of the insulating tube 810 to itsmedian point at a 45 degree angle make possible the collection of nearlyall incident rays, both direct and diffuse, from sunrise to sunset withsolar absorptive heat transfer fluid present in the center conductor830. Absorptive materials cover only half the surface of the collector,yet the collector collects nearly all the incident solar energy. When nosolar absorptive heat transfer fluid is present, the collector assemblyreflects all incident solar energy. Reflector 840, which reflects allincident solar energy, returns incident radiation back to sky.

Referring to FIG. 7, outer coating 811 may be applied to the insulatingtube 810 to block UV radiation or provide anti-reflective properties.The material forming the insulating tube 810 must allow the transmissionof solar energy to either the center conduit 830 or the reflector 840 orboth with little on no attenuation. Insulating tube 810 may be extrudedfrom glass, plastic, or other suitable solar transmissive material. Theplastic material may have any or all of the characteristics described inTable 1 below. Inner coating 813 coats the interior to reflect infraredradiation back to the center conduit 830 or to stop air from enteringthe structure when a vacuum is present on the interior of the absorber.Inner coating 813 prevents the escape of noble or inert gas such asargon, if present, to the outside air.

Outer coating 831 may be applied to the center conduit 830 to decreasepermeability to air or noble or inert gas, and to reduce the reflectionof incident energy. The material forming the center conduit 830 mustallow the transmission of solar energy to either the solar absorptiveheat transfer fluid, when present, or to or from the reflector 840 withlittle on no attenuation. Center conduit 830 may be extruded from glass,plastic, or other suitable solar transmissive material. The plasticmaterial may have any or all of the characteristics described in Table 1below. Inner coating 833 must stop solar absorptive heat transfer fluidfrom entering the material of center conduit 830. Without a coating, thesolar absorptive heat transfer fluid flowing through the center conduit830 may, over time, enter the material of the center conduit 830 andbegin the discoloration process. As the center conduit 830 discolors, itabsorbs incident solar energy even with no solar absorptive heattransfer fluid present. This effect causes the temperature of the centerconduit 830 to rise with no solar absorptive heat transfer fluidpresent. With sufficient discoloration, the temperature of the centerconduit 830 may rise to a point where the material fails. Coating 833prevents or minimizes staining, and thereby prevents or minimizesmaterial failure.

Materials of similar or differing temperature coefficients of expansionmay be utilized to form the insulating tube 810 and center conduit 830depending on the application.

The reflector 840 resides at the base of the assembly. It may be formedof a single piece of material either by cutting and bending, or it maybe extruded. Surface 841 must be mirror-like to reflect all incidentsolar energy. Coating may be applied to surface 843 to block infraredradiation from escaping. Polished aluminum, plated plastic, or othersuitable material may be used to form the reflector.

The spacer 820 serves to position the center conductor 830 within theinsulating tube 810. It also matingly receives the reflector 840 inslots 823. The spacer material may be plastic, or other suitablesubstance with high thermal resistance to minimize the conduction ofheat from the center conductor 830 to the insulating tube 810 toambient. The plastic material may have any or all of the characteristicsdescribed in Table 1 below. A coating 821 may be applied to the spacer820 to reflect incident solar energy to either the reflector 840 or thecenter conduit 830. Coating 821 may stop incident reflections toincrease transmissivity through spacer 820.

As shown in FIG. 8, center conduit 830 may take on differing dimensionsand shapes. Center conductor 830.1 maintains the circular shape anddiameter C_d but blocks solar absorptive heat transfer fluid fromentering the center of the cylinder. Fluid chambers 834.1 exist only atthe perimeter of the structure. Center conductor 830.1 delivers the samesolar absorptive properties of an open cylinder, but requires much lesssolar absorptive heat transfer fluid in the absorber. Likewise centerconductors 830.2, 830.3, and 830.4 function similarly optically, but doso with much less solar absorptive heat transfer fluid than that held byan equivalent cylinder. As the shape of the center conductor changes, somust the profile of the spacer 820. FIG. 8 illustrates both the shape ofthe center conductor and its respective spacer.

As shown in FIG. 9, reflector 840 may take on differing dimensions andshapes 840.1, 840.2 and 840.3. A differing shape may be utilized tooptimize performance for a particular application.

Referring now to FIGS. 10 and 11, the individual absorber assembly mayalso comprise end seals 827 and couplers 825. End seals 827 seal theends of the absorber 801 by creating a seal between the end of theinsulating tube 810 and the center conduit 830. The seal 827 can beattached with a suitable adhesive or other known connecting method. Theseal 827 itself may contain gaskets, joints, welds, adhesives, bellowsor other known flexible attachment methods to accept differing thermalexpansion characteristics between the center conductor 830 and theinsulating tube 810.

Coupler 825 attaches each absorber end to its respective header 860 or861 shown in FIGS. 12 and 13. The coupler 825 can be attached with asuitable adhesive, mechanically, or using another known connectingmethod. Seals between the coupler 825 and header may contain gaskets,joints, bellows, clamps or other known flexible attachment methods toaccept thermal expansion and contraction of the absorber assembly 801.

Still referring to FIGS. 10 and 11, each reflector 840 segment isapproximately L_s in length. One end of the reflector 840 plugs into aspacer 820 and the remaining end plugs into a spacer 820 or an end seal827. The combination of spacer thickness and reflector lengthestablishes dimension L_s. L_s is also the distance at which spacers 820are spaced apart to accept differing rates of thermal expansion andcontraction. With a vacuum present, the spacers 820 may be effectivelylocked into place to distribute stress along the length of the absorberinstead of just concentrating stress just at the end seals 827.Additionally, if a vacuum is present, a getter resides in the vacuumspace.

Referring to FIGS. 12 and 13, a collector assembly 800 includes N (thenumber of individual assemblies) absorber assemblies 801 connected toheader assemblies 860 and 861. The width of the absorber portion, W_abs,equals the diameter of an individual absorber assembly, I_d, multipliedby the number of absorber assemblies 801, N, found in the collector, orin equation form: W_abs=N×I_d, when the absorber tubes touch each other.To minimize cost per BTU of solar energy collected, the absorber tubesmay be spaced apart. Under this condition the W_abs becomes the sum ofthe number of absorbers utilized plus the sum of the spaces between eachabsorber. W_abs is slightly less than the overall width B. The length ofthe collector assembly 800 is slightly longer than the length of theabsorber assembly L_abs. Headers 860 and 861, which may be identical,may determine the maximum height H_abs. of the structure if theirdiameter exceeds I_d shown in FIG. 8. If the diameter of headers 860 and861 is less than I_d, then I_d sets the maximum height of the structure.Absorber assemblies 801 connect to the headers 860 and 861 with theircenters spaced I_d apart, or more. As such they may, or may not, contacteach other.

In operation, filling the center conduits of the absorber assemblies 801with solar absorptive heat transfer fluid makes the collector solarabsorptive. The solar absorptive heat transfer fluid enters throughbottom header 861, fills the absorber center conduits of the absorberassembly 801, then exits through top header 860. As noted previously,the solar absorptive heat transfer fluid flow direction may be reversed.

In one specific exemplary implementation, the length A is approximately96 inches; the width B is approximately 48 inches; the absorberthickness is approximately 0.02 inches; C_d is 0.5 inches: I_d is 1.0inch; N is 48, and L_s is 12 inches. The collector assembly may weighless than approximately 25 pounds, hold less than 5 gallons of fluid,operate with vacuum insulation, and be manufactured inexpensively.

In another specific exemplary implementation, the length A isapproximately 20 feet; the width B is approximately 10 feet; theabsorber thickness is approximately 0.02 inches, C_d is 3 inches; I_d is6 inches; N is 20; and L_s is 12 inches. The center conduit makes use ofthe configuration defined by 830.1. This collector assembly, whichcollects solar energy over an approximate 200 square foot area,assembles in a modular fashion. The entire assembly may weigh less than200 pounds, holds less than 20 gallons of fluid, operates with air asthe insulator, and may be manufactured and installed inexpensively.

Referring now to FIG. 14, headers 60 and 62 are described in greaterdetail. The bottom header 60 (being representative of the top header 62)includes a fluid reservoir portion 64 and an elongate absorberattachment portion 66 extending substantially the length of and forminga one-piece construction with the fluid reservoir portion. The bottomheader 60 has a length that is at least the width of the absorber towhich it is attached. In some embodiments, the header 60 can be formedof extruded plastic. The plastic may be optically transparent plastic.The plastic may be, for example, polycarbonate plastic. The plasticmaterial may have any or all of the characteristics described in Table 1below.

The fluid reservoir portion 64 defines a generally circular fluidpassageway 68 extending from an open end 70 to a closed end 72 (as shownin FIG. 1) of the bottom header 60. The fluid passageway 68 defined bythe interior surface of the tubular shaped portion can have a radius Iand the fluid reservoir portion 64 can have a cylindrical externalsurface with an overall radius J.

The absorber attachment portion 66 extends away from the externalsurface of the fluid reservoir portion 64 and has a generallyrectangular shape having a height K and a depth L. In some embodiments,the height K is approximately 1.0 inches and the depth L isapproximately 0.5 inches. The absorber attachment portion 66 can haveany of various other shapes, such as, for example, trapezoidal.

An elongate slot 74 is formed, such as by milling or an intrinsic slotmade by extrusion, in the absorber attachment portion 66 and penetratesan external surface of the absorber attachment portion. The slot 74extends less than the length of the header 60 and is approximately equalto or slightly longer than the overall width B of the absorber 20, has awidth approximately equal to or slightly wider than the overall depth Cof the absorber, and has a depth equal to or less than the depth L. Inthis manner, the slot 74 is configured to matingly receive the end ofthe absorber 20 within the absorber attachment portion 66. The absorbercan be retained within the elongate slot 74 through use of an adhesiveor other known bonding technique. Absorber 20 may slide into attachmentportion 66 which forms a seal with a gasket or other known “slip in”methods. When attached to each other, the absorber 20 and top and bottomheaders 60, 62 can be referred to as an absorber assembly.

In certain implementations, a fluid inlet feed slot 76 is formed in theheader in fluid receiving communication with the fluid passageway 68 andfluid expelling communication with the fluid chambers of the absorber 20when the absorber is received within the elongate slot 74. In otherwords, the fluid inlet feet slot 76 provides a channel between the fluidpassageway 68 and the fluid chambers of the absorber 20 through whichsolar absorptive heat transfer fluid is permitted to flow. The fluidinlet feed slot 76 slot extends a substantial portion of the elongateslot 74 such that each of the fluid chambers of the absorber 20 are inat least partial fluid receiving communication with the fluid inlet feedslot 76. In the illustrated embodiment, the fluid inlet feed slot 76 isa single continuous slot. In other embodiments, the fluid inlet feedslot can be multiple slots spaced apart along the length of the elongateslot.

In certain implementations, the top and bottom headers 60, 62 are platedwith a reflective layer, such as a metallic layer, to reflect solarenergy from the sun and prevent solar radiation from contacting anysolar absorptive heat transfer fluid flowing through the headers orsolar absorptive heat transfer fluid residually remaining within theheaders in the event solar absorptive heat transfer fluid is drained orotherwise removed from the panels as will be described in more detailbelow.

In certain applications, absorber assemblies such as those describedabove are placed in housings. Referring now to FIGS. 16 and 17, anembodiment of an absorber assembly housing is illustrated. In FIGS. 16and 17, a body 100 includes a base 102 and a cover assembly 104. Thebase 102 is an at least partially rigid structure having a bottom wall106, four side walls 108 extending transversely from the bottom wall andan open top end opposite the bottom wall. The bottom wall 106 and sidewalls 108 define a recess 109 within which the absorber assembly,including the headers, is positioned. In certain implementations, theabsorber assembly is coupled to the base 102 such that absorber 20 laysrelatively flat against the bottom wall 106 and the headers are matinglyreceived within and extend through apertures formed in the side walls108. This can be accomplished by forming recesses in the bottom wall 106for receiving at least a portion of the headers 60, 62. When positionedwithin the recess 109, the side walls 108 extend upwardly away from thebottom wall a distance substantially greater than the overall depth C ofthe absorber such that the upper surfaces of the side walls are elevatedabove that of the absorber and headers.

In some implementations, the absorber 20 is attached to, such asadhesively bonded to, an upper surface of the bottom wall 106 such thatthe absorber and base 102 form a unified assembly. In otherimplementations, the absorber 20 is secured to the base 100 via themating engagement between the sides 108 of the base 100 and the headerswithout any direct attachment of the absorber to the base.

The base 102 acts as an insulator to reduce conductive, convective andradiated heat losses from the solar absorptive heat transfer fluidflowing through the absorber 20. Moreover, the base 102 can providestructural support and rigidity for enduring the environmentalconditions in which the collector portion will operate. Accordingly, insome embodiments, the base 102 is made from structural foam, such aspolyurethane foam. The thickness of the bottom wall 106 and side walls108 is determined based on the desired maximum heat loss through theabsorber 20 and the R-Value of the foam. For example, in certainimplementations, the bottom wall 106 or side walls 108 can be two-inchthick inexpensive polyurethane foam having an insulating value of R-3 orgreater per inch. In one embodiment, the inexpensive foam has an R-10insulation value.

Typically, inexpensive foams such as polyurethane foam tend to melt attemperatures around 200° F. Accordingly, conventional solar collectorswould require more expensive foams capable of operating at highertemperatures, or a “buffer insulation” between the absorber and thefoam, commonly associated with such conventional collectors. As will bedescribed in more detail below, the ability of the solar energyapparatus described herein to control operating temperatures allows forthe use of lower cost foam materials relative to conventional solarcollectors.

In some embodiments, the portions of the base 102 and side walls 108that may be exposed to solar radiation are plated or painted with ametallic layer to reflect the radiation and prevent UV damage to thebase.

The cover assembly 104 includes a cover 110 coupled to the top surfacesof the side walls 108 and cover supports 112 positioned within therecess 109 between the cover 110 and the absorber 20. The cover 110 mayhermetically seal off an insulation chamber 114 defined between the sidewalls 108, bottom wall 106, cover 110, and absorber 20. In someimplementations, a seal or flexible adhesive is positioned between thecover 110 and the side walls 108 and cover supports 112 to attach thecover to the side wall and cover supports and to sealingly enclose theinsulation chamber 114. The insulation chamber 114 can include dead airor a noble or inert gas, such as Argon, to better insulate the absorberfrom the environment. The cover 110 can be sealed to the top surfaces ofthe side walls 108 with any of various adhesives or with othermechanical assemblies, such as an aluminum U-channel perimeter frame andgaskets. Such a U-channel can also provide an attachment point forcoupling the collector to a mounting surface, such as a roof.

Each cover support 112 can be an elongate beam, such as a plasticI-beam, having a first side attached to the cover 110 and a second sideopposite the first side attached to or simply touching the absorber 20.The cover supports 112 couple the cover 110 to the absorber 20 toprovide structural support to the cover 110.

As described above, in some implementations, the absorber is coupled tothe base 102 and the cover 110 via the cover supports 112 by an adhesiveor other known method of attachment e to form an integrated structuralsolar energy connector capable of withstanding harsh environmentalconditions.

In specific implementations, the absorber 20, cover 110, cover supports112 are made of a optically transparent plastic. The plastic can be anyof various plastics characterized by any of various parameter values orperformance characteristics depending on the desired application,manufacturing costs or other variables. Listed in Table 1 below areseveral clear plastic parameters, associated general descriptions of theparameter, parameter values according to various embodiments, andassociated comments. The parameters, parameter descriptions, parametervalues, and comments listed in Table 1 are associated with thecharacteristics of exemplary types of plastics that can be used to formthe plastic components of some embodiments of the solar energy apparatusdescribed herein. In other embodiments, the plastic components can bemade of plastics having performance characteristics outside of the valueranges specified in Table 1.

TABLE 1 Exemplary Parameter Description Comment Value Range Absorptivityto Ability to convert sunlight In some implementations, lower <0.05visible + UV light into heat inside the material. values are desirable.Emissivity to Ability to emit infrared. In some implementations, lower<0.2 infrared light values are desirable. Low values of emissivityreduce need for low emissivity values of the solar absorptive heattransfer fluid. Transmissivity to Ability to transmit sunlight In someimplementations, higher >0.9 visible + UV light without attenuation.values are desirable, particularly as the number of layers of plasticbetween sun and solar absorptive heat transfer fluid increases.Reflectivity to Percentage of incident light In some implementations,lower <0.05% visible + UV light reflecting off the surface of values aredesirable, particularly as the plastic. the number of layers of plasticbetween sun and solar absorptive heat transfer fluid increases. ThermalAbility of a substance to In some implementations, lower <1.5 (BTU-Conductivity conduct heat per unit length values are desirable. Lowin/hr-ft²-F.) for a given cross-sectional conductivity can provide toplayer surface area. insulation. Operating Point Low temperature at whichIn some implementations, it is <−40° F. plastic begins to beadvantageous for the plastic to functionally unstable. operate in a coldenvironment. Plastic High temperature at which a In someimplementations, higher >220° F. Deformation plastic becomesstructurally temperatures are desirable. Temperature unstable.Flammability Ability of plastic to support In some implementations,lower Low combustion. flammability values are desirable. Fluid Abilityof plastic to remain In some implementations, plastic is HighCompatibility functionally operable when compatible with solarabsorptive in contact with fluid. heat transfer fluid for at least 30years. Cost Fair market value of plastic. Post-extrusion or post-molded.<$2/Pound Lifetime Time period in which In some implementations,efficiency >10 Years plastic remains functionally may decrease by 20%after 30 years, stable with similar physical and by 10% after 10 years.and optical properties. Staining Ability of the plastic to Staining mayresult in the absorption High resist staining. of heat & fluid contact.In some implementations, small amounts of staining can be tolerated asinternal stagnation temperature fluid may be increased as a result.Surface coatings can ameliorate this requirement. Permeability toAbility of liquid to diffuse In some implementations, fluid Low liquidthrough plastic. should not permeate through the plastic. Permeabilityto air Ability of air to diffuse In some implementations, gas Low andvapor through plastic permeation through the plastic should be minimalUV resistant Ability of plastic to resist In some implementations, asHigh physical and optical damage transmissivity remains high, the fromUV rays over time. plastic is able to resist UV rays. Glue AdhesionTemperature at which In some implementations, glue stops ~250° F.plastic loses ability to working when plastic starts to loose remainadhesively bonded its properties. to glue. Hardness Resistance ofplastic to Environment can cause scratches on High indentation under astatic outer shell top surface. Such load or to scratching scratches canundesirably cause some reflection and some absorption of solar energy.Hail, or objects hurled by the wind, may damage or ruin top surface.Tensile Strength Ability of plastic to resist In some implementations,the higher High longitudinal stress without the tensile strength, thebetter so as tearing apart. to resist environmental elements, such aswind suction, and to remain secured to the collection portion. This mayreduce when exposed to UV light.

Referring to FIG. 17, in some embodiments, the cover 110 is made ofplastic that meets more performance characteristics, such as thosedescribed above, than the plastic of which the front panel 22 of theabsorber 20 is made of. Similarly, in some embodiments, the plastic ofthe front panel 22 of the absorber 20 meets more performancecharacteristics, such as those described above, than the plastic ofwhich the rear panel 24 of the absorber is made. In other words, in someembodiments, the requirements for the plastic of the cover 110 are morestringent than the requirements for the plastic of the front panel 22 ofthe absorber 20, and the requirements for the plastic of the front panel22 are more stringent than the requirements for the plastic of the rearpanel 24 of the absorber.

In some embodiments, the plastic components can be made from LexanSLX2432T, manufactured by General Electric. In some embodiments, otherplastics, such as polycarbonate and acrylic plastics, can be used.

Prior to collecting solar energy, the collection portion does notcontain solar absorptive heat transfer fluid. In this non-operationalstate, solar energy penetrates the cover 110, front panel 22, absorberchamber 34, and rear panel 24 and is reflected by the reflective layer44 to the atmosphere with minimal absorption. Further, solar energy isreflected off the reflective layers on the base 102 and bottom and topheaders. Because little to no solar energy is absorbed in thisnon-operational state, the temperature of the components of thecollection portion 12 and the overall temperature of the collectionportion remains relatively unchanged, i.e., approximately equal toambient temperature.

FIGS. 18, 19 and 20 illustrate another embodiment of a housing for anabsorber assembly. Referring to FIG. 18, an extruded collector assembly500 includes at least three components: a shell 560, headers 540, 550,which may be identical, and end caps 510, 520, which may be identical.An adhesive, or any other known bonding or coupling method, secures thecomponents in the proper position.

In the illustrated embodiment, the shell 560 includes a generallyhollow, rectangular-shaped shell having spaced-apart front and rearwalls 511, 512 and two side walls 515 positioned around opposite sidesof and coupling the front and rear walls. The shell 560 includesspaced-apart top and bottom open ends 513, 514, respectively.

The end caps 510, 520 are coupled to the bottom and top ends 514, 513,respectively, of the shell 560 to partially encapsulate the headers 540,550. The end caps 510, 520 can be attached to the ends of the shell 560with a suitable adhesive or other known connecting method. For example,although not shown, in some implementations, the shell 560, headers 540,550 and end caps 510, 520 can be coupled together using flexiblegaskets, joints, bellows, or other known flexible attachment method toseal and allow movement between the shell, headers, and end caps. Such aflexible attachment method can allow for independent movement betweenthe shell 560 and an absorber housed therein, such as when thetemperatures of the various components of the collector assembly 500 aredifferent or changed relative to each other.

As shown in FIGS. 19 and 20, the shell 560 also includes a plurality ofspaced-apart absorber support members 563 positioned between the wallsof the shell and extending transversely from the front wall 511 to therear wall 512. An absorber 562 is positioned within the shell 560 viathe support members 563 as described in greater detail below. Insulationcavities 564, 565 are formed within the shell as described in greaterdetail below.

As shown in FIG. 20, the support members 563 include absorber channels570 within which an absorber, such as absorber 562, is held in place andproperly positioned with respect to the walls of the shell. The absorber562 is similar to and includes the same general features as theabsorbers 20, 20A, 20B, 20C described above. Also, the support members563 and side walls 515 can include recesses or cut-outs 561 for matinglyreceiving a respective one of the headers 540, 550 shown in FIG. 18. Theheaders can be secured within the cut-outs 561 with a suitable adhesiveor other known connecting method.

The shell 560 allows light to transmit through to an absorber 562 and,in some embodiments, is made primarily of a UV resistant plastic orglass. The plastic material may have any or all of the characteristicsdescribed in Table 1 above. As with the absorbers previously described,the absorber 562 contains solar absorptive heat transfer fluid when in asolar energy absorption mode and does not contain solar absorptive heattransfer fluid when in a solar energy reflection mode.

The shell 560 includes upper and lower insulation cavities 564, 565,respectively. The upper insulation cavities 564 are defined between thefront wall 511 of the shell and the absorber 562 and the lowerinsulation cavities are defined between the rear wall 512 and theabsorber. The cavities 564, 565 provide dead air insulation above andbelow the absorber 562, respectively. In some embodiments, the lowerinsulation cavities 565 can be filled with an insulative material, suchas foam beams or solid foam, to improve bottom insulation performanceand strengthen the shell 560.

The front and rear panels of absorber 562 have a thickness D, which isdefined above in relation to FIG. 3. Each support member 563 has aheight that is substantially greater than its thickness. In certainimplementations, the thickness of each support member 563 is smallerthan the thickness D of the panels of the absorber 562. The reducedthickness of the support members 563 can relieve stresses associatedwith thermal expansion of the absorber 562 when the absorber 562contains hot circulating solar absorptive heat transfer fluid and theshell 560 is cold. Since a tall, but thin, member offers high thermalresistance per unit length, the ratio of the height of supports 563divided by the width of the supports may be large to minimize conductionof heat from the absorber 562 to the outer shell 560. As shown in FIG.20, the support member 563 are spaced-apart a distance H from eachother.

In some implementations, the thickness of the shell walls is greaterthan the thickness D of the absorber front and rear panels. Such aconfiguration can improve the structural performance of the shell andallow the shell to better withstand adverse environmental conditions.

As shown in FIGS. 18 and 19, the shell 560 has a length A, a width B,and a height L. In certain implementations, the length of the absorber562 is slightly less than the length A of the shell 560 and the width ofthe absorber is slightly less than the width B of the shell. Configuringthe absorber to be slightly shorter and narrower than the shell providesa space to attach the headers 510, 520 and provides space for horizontaland vertical thermal expansion when the headers are connected toabsorber 562. Like the absorber described above, absorber 562 has aplurality of fluid channels through which an absorptive fluid can flow.Each channel has a width S and a depth or height E.

In one specific exemplary implementation, the length A is approximately96 inches; the width B is approximately 48 inches; the thickness D isapproximately 0.01 inches; the height E is approximately 0.10 inches;the width S is approximately 0.25 inches; the distance H isapproximately 3.00 inches; and the height L is approximately 3.00inches. The collector assembly 500 may weigh less than approximately 15pounds, hold less than approximately 1.5 gallons of solar absorptiveheat transfer fluid, and be manufactured inexpensively.

FIGS. 21 through 28 illustrate still another embodiment of a housing foran absorber assembly. As shown in FIGS. 21, 21A and 22, a shell 702serves as a housing for a an absorber 701.

As shown in FIG. 21, the absorber 701 includes absorber panel 721,headers 760, 761 at the ends of the absorber panel 721 and a pluralityof flex beams 741 coupled to the absorber panel 721, extending thelength of the absorber panel and aligned perpendicularly to the headers760, 761. FIG. 21A illustrates a front view of the absorber assembly.The absorber 701 consists of the absorber panel to which header pipes760 and 761 attach at each end using an adhesive or other suitablemethod. Flex beams 741, spaced distance H apart, attach to the absorberpanel 721 on the top and bottom surfaces using an adhesive or othersuitable method. Distance L_abs must be less than A shown in FIG. 27.Distance W_abs must be less than B shown in FIG. 22. The height of theabsorber must be less than L shown in FIG. 22.

As shown in FIG. 22, the shell 702 includes a generally hollow,rectangular-shaped shell having spaced-apart top and bottom panels 711,731 and two side panels 751 and 752 positioned on opposite sides of andconnecting to the top and bottom panels using side connecting beams 750in four locations. Tracks 740, spaced H apart, attach to the top andbottom panels using an adhesive or other suitable method.

FIGS. 23 and 24 illustrate an expanded front view of the left side ofthe collector assembly 700 with headers 760 and 761 removed and a frontview of the collector assembly 700 with headers 760 and 761 removed,respectively. The top panel 711 passes solar energy to the absorberpanel 721 while providing insulation and infrared reflectivity. Theabsorber panel 721 contains a solar absorptive heat transfer fluid whencollecting solar energy. When not collecting solar energy, the absorberpanel 721 contains no solar absorptive heat transfer fluid. The bottompanel 731 provides insulation and infrared energy reflectivity. Sidepanel 751 provides insulation and infrared energy reflectivity. Cornerbeams 750 connect the top panel 711 to the left side panel 751 and rightside panel 752. Corner beams 750 also connect the bottom panel 731 tothe left side panel 751 and right side panel 752. Shell tracks 740attach, by adhesive or other suitable method, to the top panel 711 andbottom panel 731. The distance H separates one track from the other.Absorber flex beams 741 attach, by adhesive or other suitable method, tothe top and bottom surfaces of absorber 721. The distance H separatesone flex beam from the other. The track 740 matingly receives flex beam741 to connect the shell assembly 702 to the absorber assembly 701 whileproviding movement within the structure to adapt to temperature changeand environmental stress.

Each flexible beam 741 has a length that is substantially greater thanits thickness. Likewise, the length of the flexible beam 741, because ofits serpentine shape, significantly exceeds its height. In certainimplementations, the thickness of each support member 741 may be madeconsiderably less than the total length of the serpentine supportmember. Since a long, but thin, member offers high thermal resistanceper unit length, the ratio of the length of flexible beam 741 divided bythe material thickness of the supports may be large to minimizeconduction of heat from the absorber 721 to the outer panels 711 and731. By intention, they form a very poor thermal connection to track740.

While the flexible beam 741 is shown having a serpentine shape, anyother flexible shape which accommodates lateral stress without failuremay also be used for the flexible beam. For example, the flex beams maybe comprised of two flexible beams opposing each other and bowing awayfrom each other, like two opposing leaf springs.

FIG. 25 illustrates the relationship between the top panel 711, theabsorber 721, the bottom panel 731 and the tracks 740 and flex beams 741in three dimensional detail. With solar absorptive heat transfer fluidpresent, the temperature of the absorber 721 rises when exposed to solarradiation. A rising temperature produces expansion of the absorber inall dimensions. To accommodate expansion in the length of the absorber,the flex beam 741 slides within the track 740. The serpentine nature ofthe flex beam readily accepts changes in dimension of width and height.The compressive and expansive properties of the flex beam accept andadapt to ambient temperature variations, wind load, and impact fromnatural and man-made objects.

Referring back to FIGS. 23 and 24, one embodiment uses coatings andadditives upon and within panel 711 to optimize performance. An ultraviolet, UV, blocker with antireflective properties coats the top surface710 of the top panel 711. This coating protects the top panel 711 andall components below from the harmful effects of UV radiation. Theantireflective nature of the coating maximizes the amount of solarenergy passing into the absorber panel 721, when filled with solarabsorptive heat transfer fluid, over a range of incident sun angles. Aninfrared coating may also be applied to the top surface 710.

An infrared reflective coating 712 may be used to stop heat from beingradiated to outside space when the collector 700 collects solar energy.The coating 712 passes incident energy to the absorber 721 whilereflecting infrared emitted from the absorber 721 back to the absorber.The bottom surface of the top panel 711 may also include an ultravioletblocker.

Specific coatings on the interior chambers, formed by E_shell andS_shell, of the top panel 711 determine part of the heat losscharacteristics and thereby part of the insulation characteristics ofthe top panel 711. An optically transmissive coating applied to theinterior chambers allows the top panel 711 to be filled with a noble orinert gas, such as argon, or support a vacuum to increase the thermalresistance over air filling the chamber. The interior chambers may alsobe made from an optically transmissive material, thereby eliminating theneed for a coating. One embodiment uses a coating which entraps a nobleor inert gas in the top panel 711. Significant increases in thermalresistivity occur under such a condition. A similar, or possiblydifferent, coating may be applied to prevent gasses from entering thetop panel 711. This coating permits the creation of a vacuum. In case ofa vacuum, a getter may be inserted inside chambers of the top panel 711Very high thermal resistance exists with a vacuum present on theinterior of the top panel 711. Heat only conducts outward through thethin vertical support members of 711, where the ratio of E_shell to thethickness, D is large. The top panel's thermal conductivity is smallcompared to conventional solar collector top glazing, which isfrequently glass. The top panel material may be low thermal conductivityplastic. The interior chambers may also be coated with an anti-stainingmaterial.

Coatings and additives upon and within bottom panel 731 optimize thermalperformance. An infrared reflective coating 732 may be used to stop heatfrom being radiated to space when the collector 700 collects solarenergy. The coating 732 returns infrared emitted from the absorber 721back to the absorber. Coating 732 may also be an ultra violet, V,blocker with antireflective properties.

Coating 730 provides additional infrared reflectivity and may also haveantireflective properties. Coating 730 and 732 may or may not beidentical.

Specific coatings on the interior chambers, formed by E_shell andS_shell, of the bottom panel 731 determine part of the heat losscharacteristics and thereby part of the insulation characteristics ofthe bottom panel 731. A coating applied to the interior chambers allowsthe bottom panel 731 to be filled with a noble or inert gas, such asargon, or support a vacuum to increase the thermal resistance over airfilling the chamber. One embodiment uses a coating which entraps a nobleor inert gas in the bottom panel 731. Significant increases in thermalresistivity occur under such a condition. A similar, or possiblydifferent, coating may be applied to prevent gasses from entering thebottom panel 731. This coating permits the creation of a vacuum. In thecase of a vacuum, a getter may be inserted inside chambers of bottompanel 731. Very high thermal resistance exists with a vacuum present onthe interior of the bottom panel 731, heat only conducts outward throughthe thin vertical support members of 731, where the ratio of E_shell tothe thickness, D is large. The thermal conductivity of the bottom panelis comparable to the thermal conductivity of the insulation commonlyused on the bottom sides of the conventional solar collectors. Thebottom panel material may be low thermal conductivity plastic. Theinterior chambers may also be coated with an anti-staining material.

The side panel 751, while differing in dimension from the bottom panel731, uses similar coatings and exhibits similar performance.

While not shown in any drawings, insulation (fiberglass, foam, or othersuitable type) may be inserted in the spaces between the absorber 721and the bottom panel 731 to further increase collector efficiency. Thisinsulation must be expandable and compressible or allow enough space tonot interfere with the operation of the flex beams 741. Insulation maybe applied outside of shell 702 on the bottom 731 and the sides 751 and752 for additional heat loss reduction.

Coatings and additives upon and within the absorber panel 721 optimizeperformance. The antireflective nature of the coating maximizes theamount of solar energy passing into the absorber panel 721, when filledwith solar absorptive heat transfer fluid, over a range of incident sunangles. A reflective coating 722 or reflective material applied byadhesive or other know means reflects the full spectrum of incidentenergy upwards back to sky with no solar absorptive heat transfer fluidpresent in the absorber 721. The combination of solar absorptive heattransfer fluid and a bottom reflective surface make the absorber 721either solar absorptive when the solar absorptive heat transfer fluid ispresent, or solar reflective when no solar absorptive heat transferfluid exists in the absorber 721.

A coating on the interior chambers, formed by E_abs and S_abs, preventsthe absorption of the solar absorptive heat transfer fluid into thematerials that form the absorber 721. Without any coating as thecollector ages, the solar absorptive heat transfer fluid may enter thematerials forming the absorber 721 and begin a discoloration process. Asthe absorber 721 discolors it absorbs incident solar energy even with nosolar absorptive heat transfer fluid present. This effect causes thetemperature of the absorber 721 to rise when exposed to solar radiation.With sufficient absorption of solar absorptive heat transfer fluid, thetemperature of the absorber 721 may rise to a point where the materialsforming the absorber 721 fail. The interior coating of the absorber 721prevents staining and thereby material failure.

FIGS. 26, 27 and 28 illustrate a top, side and three dimensional view ofthe complete assembly, respectively. Corner beams 750 couple togetherthe sides of the shell and flex beams 741 mate with shell tracks 740 toposition the absorber inside the shell. End caps 770, 771 are coupled tothe bottom and top ends of the shell for the purpose of partiallyencapsulating the headers 760, 761, and the entire absorber assembly.The end caps 770, 771 can be attached to the ends of the shell with asuitable adhesive or other known connecting method. For example,although not shown, in some implementations, the shell headers 760, 761and end caps 770, 771 can be coupled together using flexible gaskets,joints, bellows, or other known flexible attachment method to seal andallow movement between the shell, headers, and end caps. Such a flexibleattachment method can allow for independent movement between the shelland absorber, such as when the temperatures of the various components ofthe collector assembly are different or changed relative to each other.

With specific reference to FIG. 27, openings 753 provide access toheaders 760,761. Connecting pipes with suitable couplers attach throughthese openings. In this manner, one collector assembly 700 may beconnected to another collector assembly 700, or headers 760 and 761 maybe connected to their respective feed and return lines. With end caps770 and 771 removed, the couplers may be attached to the headers bymechanical means, or by using an adhesive or other suitable method.

As shown in FIGS. 24, 26 and 28, the collector 700 has a length A, awidth B, and a height L. In all implementations, the length of theabsorber 701 is slightly less than the length A of the shell 702 and thewidth of the absorber is slightly less than the width B of the shell.Configuring the absorber to be slightly shorter and narrower than theshell provides a space to attach the headers 760, 761 and provides spacefor horizontal and vertical thermal expansion when the headers areconnected to absorber 721. Like the absorber described above, absorber721 has a plurality of fluid channels through which an absorptive fluidcan flow. As shown in FIG. 23, each channel has a width S_abs and adepth or height E_abs.

In one specific exemplary implementation, the length A is approximately96 inches; the width B is approximately 48 inches; the materialthickness D is approximately 0.01 inches; the height E_abs isapproximately 0.16 inches; the width S_abs is approximately 0.16 inches;the width S_shell is approximately 0.50 inches and E_shell isapproximately 0.50 inches; the distance H is approximately 12.00 inches;and the height L is approximately 3.00 inches. The collector assembly700 may weigh less than approximately 25 pounds, hold less thanapproximately 3.0 gallons of solar absorptive heat transfer fluid, andbe manufactured inexpensively.

In other embodiments described herein, the absorber is built into thehousing. Referring to FIGS. 29 and 30, a collector 200 having acollection portion 202 is shown. Collection portion 202 is similar tocollection portion 12, but is configured to circulate solar absorptiveheat transfer fluid in a top to bottom direction rather than a bottom totop direction as with collector 10. The collection portion 202 includesa body 210 having a foam base 212, three large elongate foam ribs 214,four small elongate foam ribs 215, two large elongate foam side ribs222, and two small elongate foam side ribs 223. The number of largeelongate form ribs and small elongate foam ribs may be greater than orless than the stated numbers and other materials similar to foam mayalso be used. The surfaces of the foam components may also be coatedwith a material making the foam impermeable to circulating fluid.

Base 212 is generally rectangular with a rear wall 216, a top wall 217,and a bottom wall 219 projecting transversely from the rear wall. Anabsorber recess 220 is defined between the rear wall 216 and the sidewalls 218 shown in FIG. 30. Top and bottom headers 242, 244 are locatedat the top and bottom end 230, 232, respectively. Arrow 254, 255 and 256indicate the direction of flow of solar absorptive heat transfer fluidwhen the collector is in operation.

Referring to FIG. 31, the small elongate foam ribs 215 projecttransversely away from rear wall 216 and extend the length of the recess220 from the top wall 217 at a top end 230 of the body 210 to the bottomwall 219 at a bottom end 232 of the body 210 as shown in FIG. 29. Thesmall elongate foam ribs 215 extend generally parallel to each other andthe side ribs 223 from the top end 230 to the bottom end 232 shown inFIG. 29. Each of the small elongate foam ribs 215 are spaced-apart fromthe side ribs 223 a distance “n times D1” where n is the number of smallelongate foam ribs between the foam rib in question (including itself)and a side rib 223.

The large elongate foam ribs 214 project transversely relative to therear wall 216 and extend from the top end 230 to the bottom end 232 ofthe body 210 shown in FIG. 29. Each large elongate foam rib 214 isaligned with a small elongate foam rib 215, positioned between twoadjacent small elongate foam ribs 215, and extends generally parallel tothe adjacent small elongate foam ribs. Each of the large elongate foamribs 214 are spaced-apart from the side ribs 222 a distance “n times D2”where n is the number of large elongate foam ribs between the foam ribin question (including itself) and a side rib 222. In the illustratedimplementation, D2 is greater than D1.

Referring to FIGS. 31 and 32, the collection portion 202 includes aninner optical layer 240 supported by and attached to the small elongatefoam ribs 215 and side ribs 223. In the illustrated implementation, theinner optical layer 240 is positioned above the small ribs 215, 223 suchthat several fluid chambers 229 are defined between the base 216, theinner optical layer 240 and adjacent small ribs 215, 223. The fluidchambers 229 are in fluid receiving communication with the top header242 and fluid expelling communication with the bottom header 244 shownin FIG. 29.

The collection portion 202 also includes an outer optical layer 250supported by and attached to the large elongate foam ribs 214 and sideribs 222. The optical layer 250 and dead-air, or inert gas in someimplementations, located within insulation chambers 252 defined betweenthe inner optical layer 240, the outer optical layer 250, and adjacentlarge ribs act as an insulator in the same manner as the cover 110 andinsulation chamber 114. As with collection portion 12, the inner andouter optical layers 240, 250, which may be made of a plastic materialhaving some or all of the characteristics described in Table 1 above,provide two layers of insulation between the environment and the solarabsorptive heat transfer fluid circulating through the fluid chambers.The two layers of insulation assist in keeping heat stored in the solarabsorptive heat transfer fluid from being lost via radiation,conduction, or convection into the outside environment.

In some embodiments, the base 212, large ribs 214, 222, and small foamribs 215, 223 are plated with a reflective layer or coating to reflectsunlight to keep the components of the collection portion 202 cool and,in some embodiments, keep ultraviolet light from damaging the plastic orinsulation. Additionally, the reflective layer can enhance solar energyabsorption by redirecting the sunlight striking the ribs into solarabsorptive heat transfer fluid contained within the fluid chambers,thereby increasing the overall efficiency of the collector 200.

Referring to FIG. 33, in operation, solar absorption fluid, such blackfluid 270, enters the top header 242 as indicated by directional arrow254 via a pump and lines much like the collector 10 as previouslydescribed. Once the header 242 is filled up to the level where itsliquid meets the recess, fluid overflows from the header and into thefluid chambers. The fluid is then continuously gravity fed downwardthrough the fluid chambers as indicated by directional arrows 255 fromthe top end 230 to the bottom end 232, collecting solar energy along theway, until it collects in and exits from the bottom header 244 asindicated by directional arrow 256.

FIG. 34 illustrates another embodiment of a combined housing andabsorber. As shown in FIG. 34, a solar energy collector 400 includes acollection portion 402 with four layers of extruded plastic or glass,e.g., a top layer 410, bottom layer 412, upper middle layer 414, andlower middle layer 416. The plastic material may have some or all of thecharacteristics described in Table 1 above. Additionally, the plasticmay be coated with a material to make the plastic impermeable to vaporand air.

The top layer 410 and upper middle layer 414, and bottom layer 412 andlower middle layer 416, can be coupled together in a spaced apartrelationship via a plurality of spacers 420. The spacers 420 can run alength of the collection portion 402 such that vacuum chambers 422 areformed between respective layers and spacers. The air within the vacuumchambers 422 can be vacated to form a vacuum within each of the vacuumchambers. Getters may be placed inside each vacuum chamber. The vacuumchambers may also be chambers filled with dead air, inert gas or noblegas, rather than a vacuum.

The upper and lower middle layers 414, 416 are coupled together in aspaced apart relationship via absorption chamber spacers 424. As withthe spacers 420, the absorption chamber spacers 424 can extend a lengthof the collection portion 402 such that fluid chambers 426 are definedbetween the upper and lower layers 414, 416 and respective spacers 424.Although not shown, headers can be implemented at respective inlets andoutlets to the chambers 426 and solar absorptive heat transfer fluid canbe pumped into the chambers 426 via one header and out of the chambersvia another header. Top and bottom headers may be recessed to allow onlychamber 426 to connect to top and bottom headers.

As the solar absorption fluid flows between the headers and through thefluid chambers 426, it collects solar energy. The vacuum chambers 422are vacated of air to create a vacuum that provides an insulatingbarrier for preventing conducted and convective heat losses from thesolar absorptive heat transfer fluid as it flows through the fluidchambers 426.

In some implementations, the fluid chambers 426 have a depth ofapproximately 0.05 inches.

The collection portion 402 has a width Q and an overall depth R. In someimplementations, the width Q is approximately 6.0 inches and the depth Ris approximately 0.5 inches.

Although not specifically shown, in some implementations, the collectionportion 402 may have foam insulation, e.g., a body, surrounding sides430, ends (not shown) and bottom layer 412 of the collection portion.Also, a reflective layer 432, such as a plated metallic layer, may becoupled to the outer surface of the bottom layer 412 to reflect solarlight when the fluid chambers 426 are not filled with solar absorptionfluid. Further, although the implementation of the solar energycollector 400 illustrated in FIG. 34 has four layers, in otherimplementations, the solar energy collector can have more or less thanfour layers.

In some embodiments, one or more collection portions can be arranged inseries or parallel and coupled to each other directly or via commonheaders to effectively provide a wider solar energy absorption area.

Referring now to FIGS. 35-39, a modular solar collection system 600according to one embodiment is shown. Similar to the collection systemsdescribed above, modular solar collection system 600 collects energythrough use of a circulating or absorptive fluid, such as black fluid.The modular solar collection system 600 is configured to be easilyconnectable to adjacent collection systems as will be described in moredetail below.

Referring to FIG. 35, the collector assembly is shown with eachcomponent of the assembly separated and also with each component stackedtogether into the collector assembly. Collector assembly 600 includes anabsorber assembly 610, frame assembly 620, foam assembly 630, gasket640, clear top cover assembly 650, and top retainers 660.

Referring now to FIGS. 36, 37 and 38, illustrating a side, front and topview of the collector assembly, the absorber assembly 610 is similar tothe absorbers 20, 20A, 20B, 20C described above. Generally, the absorberassembly includes an absorber 613 coupled to two headers 611, 612 usingadhesive or other known coupling techniques. The absorber 613 can bemade of a clear extruded material, such as UV protected polycarbonateplastic having characteristics as described in Table 1 above, and havean overall thickness C. In some instances, the thickness C can beapproximately 0.25 inches, and in other instances, the thickness C canbe less than or greater than 0.25 inches. The absorber assembly 610includes one or more fluid chambers (not shown) such as described above.In certain implementations, the fluid chambers of the absorber assembly610 can contain approximately one gallon of solar absorptive heattransfer fluid.

The frame assembly 620 includes a right side beam 622, left side beam626, top beam 627, bottom beam 621, header mounting apertures 623, andtop cover assembly supports 624. The header mounting apertures 623receive the headers of the absorber assembly 610 and allow access to theheaders from a location external to the collection system 600. The topcover assembly supports 624 are spaced-apart along the right and leftside beams 622, 626 at appropriate intervals to align with matingstructures on the top cover assembly as will be described in more detailbelow.

The foam assembly 630 comprises a generally rectangular sheet of foam631 having a thickness that can be approximately half a total thicknessR of the collector assembly 600. In some implementations, sealantmaterials can be applied to the surfaces of the sheet of foam 631 toreduce out gassing and enhance collector performance. In someimplementations, the foam is encapsulated inside a high permeabilitysubstance such as plastic. The top surface of the sheet of foam 631 canalso be coated with a reflective material 635 to reflect incident solarenergy to the sky when fluid is not present in the absorber assembly 610such that the internal temperature of the collector 600 is near ambienttemperature. When fluid is present in the absorber assembly 610, thereflective material 635 can, in some implementations, effectivelyincrease the absorption path length through the fluid by a factor oftwo. More specifically, incident solar energy that enters the fluid, butis not absorbed, reflects off the reflective material 635 and passesthrough the fluid a second time for reabsorption.

In some implementations, a moisture barrier 636 can be coated on thebottom of the sheet of foam 631 and right and left side beams 622 and626 to prevent moisture from entering the foam and the assembly 600. Thefoam assembly 630 can have stepped ends or recesses 632, 633 forreceiving the headers of the absorber assembly 610 and allowing forthermal expansion and contraction of the absorber as it heats up andcools down.

The frame assembly 620 is coupled to the foam assembly 630 and extendsabout a periphery of the foam assembly. In certain implementations,adhesives secure the frame assembly 620 to the foam assembly 630 toincrease the overall strength of the collection assembly 600 and providea seal between the frame assembly and the foam assembly.

In the illustrated implementation, the absorber assembly 610 rests upon,but is not attached to, the foam assembly 630. The foam assembly 630vertically centers the absorber assembly 610 within the frame assembly620. The absorber assembly 610, e.g., the absorber 613 and attachedheaders 611, 612, has a length less than the length A of the collectorassembly 600 and a width less than the width B of the collector assemblysuch that the absorber assembly can fit into and float within the frameassembly 620. The floating nature of the absorber assembly 610accommodates the thermal expansion and contraction of the absorber ashot solar absorptive heat transfer fluid is either added (expansion) orremoved (contraction).

The top cover assembly 650 comprises a generally rectangular plasticsheet having a front wall 654, a top wall 652, and a bottom wall 651. Insome implementations, the plastic may be polycarbonate and may have someor all of the characteristics described in Table 1 above. The top coverassembly 650 also includes beams 653 secured to an inner surface of thefront wall 654 and extending parallel to the top and bottom walls 652,651. The beams 653 can be secured to the front wall 654 by an adhesiveor other known fastening method. The beams 653 are sized and shaped tobe matingly received and laterally secured in slots formed in the topcover assembly supports 624 of the frame assembly 620. The top andbottom walls 652, 651 can, in some implementations, provide a weatherseal and function as an end beam as well.

The collector assembly 600 includes a pair of top retainers or brackets660 that at least partially secure the top cover assembly 650 to theframe assembly 620. In certain implementations, the top retainers 660each include a central portion that extends lengthwise across the topcover assembly 650 between the top wall 652 and the bottom wall 651 andtabs that extend perpendicularly from the central portion and overlapthe top and bottom walls. The tabs can be secured to the frame assembly620 through use of a fastener or other coupling technique. When securedto the frame assembly 620, the top retainers 660 secure the top coverassembly 650 in compression. Accordingly, the top retainers 660 preventfront to rear motion of the top cover assembly 650 relative to the frameassembly 620 and the mating engagement between the support beam 653 andthe cover assembly supports 624 prevents side to side motion of the topcover assembly relative to the frame assembly. In this manner, the topcover assembly 650 can maintain its structural integrity during severeweather conditions and not make contact with the absorber assembly 610.

As has been described above, the foam assembly 630 seals a bottom of thecollector assembly 600, frame 620 seals the sides of the collectorassembly, and the top 650 in conjunction with a gasket 640 seals the topof the assembly. Top retainers 660 compress the top 650 into the gasket640 to form a complete perimeter seal.

In an exemplary implementation, the length A is approximately 102inches; the width B is approximately 52 inches; the thickness C isapproximately 0.16 inches; and the depth R is approximately 4 inches.The beams of the frame assembly 620 can have a thickness ofapproximately 1 inch and a height of approximately 4 inches. The supportbeams 653 can have a thickness of approximately 0.25 inches and a heightof approximately 1.25 inches. The collector assembly 600 according tothis exemplary implementation, can weigh less than approximately 30pounds and may hold less than 3 gallons of solar absorptive heattransfer fluid.

In another exemplary implementation, the length A is approximately 106inches; the width B is approximately 52 inches; the thickness C isapproximately 0.25 inches; and the depth R is approximately 3.5 inches.The beams of the frame assembly 620 can have a thickness ofapproximately 1 inch and a height of approximately 4 inches. The foamassembly 630 is approximately 1.5 inches thick and the frame 620 is madefrom 1.0 inch by 3.5 inch PVC foam board. The absorber fluid chambershave a height E of approximately 0.25 inches and a width S ofapproximately 0.25 inches such that the absorber holds approximately 5gallons of fluid.

In some embodiments, the collector assembly 600 provides severaladvantages. For example, collector assembly 600 is made of inexpensivematerials such that the collector assembly is light, strong,weather-proof, easily installed, and aesthetically appealing. Theextensive use of plastics and foam in the collector assembly reduces theweight of the assembly, which can lend to easy installation versusheavier collectors. Employing securing structures extending in thedirections of dimensions A and B, as well as securing many of thecomponents together using adhesives and fasteners, results in astructurally strong and long-lasting collector assembly. The fullperimeter gasket, folded down top cover assembly, and the use of sealantadhesives produce weather tight seals. Additionally, the configurationof the collector assembly 600 resists rain, snow, sleet, and icebuild-up by providing smooth top surfaces on which accumulation willreadily slide. Also, as described above, the floating nature of theabsorber facilitates connecting adjacent units (as will be describedbelow) using simple flexible pipe. Aesthetically, there are no visiblecomponents other than the case top and sides. For example, all pipes,connectors, and roof mounts remain out of sight under the top coverassembly 650.

As shown in FIG. 39, in certain implementations, the modular solarcollection system 600 is connectable, such as in parallel, to othercollector assemblies. In one specific implementation, such as shown inFIG. 38, three collection systems 600 are connected in parallel.Although three collection systems interconnected are shown, in otherimplementations, fewer or more than three collection systems can beconnected together in parallel or otherwise. Flexible couplers (notshown) extending through holes 623 connect one collector assembly 600 toanother connector assembly 600. In some implementations, ten or morecollector assemblies can be connected together. In some instances,on-site assembly of a collector assembly array can be accomplished inless than a day by a crew of two. In the event an additional collectorassembly is needed, such as when more solar surface area coverage tocapture more energy is desired, one or more additional collectorassemblies can be easily connected in any of various configurationsknown in the art.

The collector assembly 600 provides a combination of excellent energycollection performance, low manufacturing cost, and low installationcost. Accordingly, the collector assembly 600 can provide a considerablebenefit to heat energy consumers.

Turning now to FIG. 40, and according to one embodiment of a drainbacksystem with a fluid reservoir 154 contained within the thermal storagemass 152, a solar energy apparatus, e.g., solar energy collector, orcollection system, 10, includes a solar energy collection portion 12.The collection portion 12 includes an absorber 20, a bottom header 60, atop header 62, and a frame 100. The solar energy collection portion 12has a generally rectangular configuration although any other suitablegeometry could be used.

The collector 10 includes a solar energy distribution system 14. Thesolar energy distribution system 14 includes a fluid pump 150, thermalstorage mass 152 and fluid reservoir 154 in thermal communication witheach other via heat exchanger 158. In some implementations, lines, asused herein, can be insulated conduits or pipes.

In operation, solar absorptive fluid, e.g., black fluid, which is storedin the reservoir 154, is pumped via lines 156 by pump 150 into thebottom header 60 at the open end 70 as indicated by directional arrow161. Black fluid entering the bottom header 60 flows through the fluidpassageway of the header and is initially contained within the header bythe closed end 72 of the header. The fluid passageway of header 60 fillswith black liquid until the fluid reaches the level of the infeed slot76 shown in FIG. 14. Further pumping of fluid into the fluid passagewayof the header causes fluid to flow through the slot 76 and into theabsorber chambers. As pumping continues, fluid flows upward in thedirection indicated by directional arrow 163 from the bottom end 38 ofthe absorber to the top end 42 until the entire absorber fills withblack fluid as shown in FIG. 2.

Once the absorber chambers are filled, further pumping causes fluid toenter the top header 62 via an outfeed slot (not shown) similar to theinfeed slot 76. The fluid passageway of the top header 62 fills withfluid in the same manner as the bottom header 60 until the passageway isat least partially full and fluid exits the top header via its open end70 in a direction indicated by directional arrow 165. From the open end70 of the top header 62, the fluid enters fluid line 157 and flows intoheat exchanger 158, then returns to the reservoir 154. Storage mass 152,which can be any thermal mass commonly known in the art, stores heat foruse by other devices (not shown) attached to the system.

Although FIG. 40 shows operation with only one collector assembly 12, inother embodiments, several collector assemblies may be connected inseries or in parallel.

In operation, the pump 150 cyclically pumps fluid through the systemsuch that fluid continuously flows upward through the absorber chambers.As black fluid flows through the absorber 20, solar energy from the sunis absorbed in the black fluid as thermal energy. The thermal energy isthen transferred to the thermal energy storage mass 152 via header 62and transport pipe 157, and heat exchanger 158.

The black, or sufficiently high absorptivity, fluid can have any ofvarious properties or performance characteristics depending on theapplication or the structure of the collector, such as the depth of theabsorber chambers. For example, listed in Table 2 below are severalsolar absorptive heat transfer fluid parameters, associated generaldescriptions of the parameters, parameter values according to variousembodiments, and associated comments. The parameters, values, andcomments listed in Table 2 are merely examples of parameters andparameter value ranges of implementations of solar absorptive heattransfer fluid that can be used in the solar energy apparatus describedherein. In other embodiments, the solar absorptive heat transfer fluidcan have performance characteristics that are not listed in Table 2 orfall outside of the value ranges specified in Table 2.

TABLE 2 Exemplary Parameter Description Comment Value Range AbsorptivityA measure of the ability to In some implementations, higher >0.95convert sunlight into heat. absorptivity is desired. Emissivity Abilityto emit infrared. In some implementations, lower <0.90 emissivity isdesired. Evaporation The relative amount of Evaporation can degradeoptical Very Low energy required to convert performance. Moreover,evaporated a liquid into a vapor per gases may escape and result influid unit mass. loss. In some implementations, evaporation is minimal.Pigments or Materials with high In some implementations, higher HighlyDyes absorptivity that dissolve absorptivity is desired. Moreover,Absorptive or stay in suspension pigments and dies should be selectedwithin a liquid that do not evaporate, adhere to surfaces, or hampercirculation. Liquid Abrasion Ability of fluid to Generally, the liquidshould not Very Low frictionally wear down significantly wear out fluidother materials through containing structures or the pigments fluidflow. or dyes. Specific Heat Heat capacity per unit In someimplementations, higher >0.4 mass values for specific heat are desired.BTU/Pound- deg F. Density Unit mass or weight of a Not directly aperformance measure Not applicable material (in this case a liquid) perunit volume. Density - A measure of the heat In some implementations,high <50 Specific Heat energy added per unit “Density times SpecificHeat” is BTU/cubic Product volume of a material to desirable because itdirectly effects foot of raise its temperature 1 the required flow rateand thereby the substance degree F. resulting pump size. Thermal Abilityof a fluid to In some implementations, high >4.0 (BTU- Conductivityconduct heat-per unit thermal conductivity is desired, suchin/hr-ft²-F.) length for a given cross- as proximate a thermal mass.sectional surface area. Freezing Point Temperature at which fluid Insome implementations, a low <−40° F. freezes. freezing point is desiredfor various reasons, such as freezing problems which break pipes.Boiling Point Temperature at which fluid In some implementations,higher >200° F. boils. boiling points are preferred to reduce danger,increase safety and prolong operability of the collector. ViscosityAbility of fluid to resist its In some implementations, low Low ownflowing. viscosity values are desirable. Higher values may require alarger pump. Generally, aging and liquid temperature are factors thatdetermine the viscosity of the fluid. Surface Tension Ability of fluidto form Low surface tension allows the fluid Low tension on its surfacethat to fully drain from the absorber, holds itself together. results inless capillary action and wicking. This reduces problems of pipesbreaking during freezing. Flammability Ability of fluid to support Insome implementations, lower Low combustion. flammability values aredesirable. Plastic Ability of fluid to remain In some implementations,plastic is High Compatibility functionally operable compatible withsolar absorptive heat when in contact with transfer fluid for at least30 years. plastic. Cost Fair market value of fluid. In someimplementations, lower fluid <$10/gallon cost is desirable. LifetimeTime period in which fluid In some implementations, the fluid is >3Years remains functionally stable replaced once every three years. Incertain implementations, the controller includes a computer thatprovides a notification to replace the fluid. Staining Propensity of thefluid to Staining may result in the absorption Low stain. of heat duringstagnation which may cause plastic to break over a period of time.Permeability Ability of fluid to In some implementations, the Lowpermeate through plastic. permeability of the fluid is desirably low.This is a function of the fluid and the plastic of Table 1 together.Resistant to O₂ Ability of fluid to resist In some implementations,fluid is High and UV oxidization and UV generally resistant tooxidization and damage. UV damage. Eco-friendly Measure of negativeGenerally desirable to reduce long- Low impact on environment. andshort-term harm to environment. Future Ability to change fluids as Insome implementations, selecting a Medium Expandable better ones aredeveloped. fluid that resists staining and lowers permeability allowsfuture fluids to be compatible with the original absorber with perhapshigher performance since past residues will be minimized.

In some embodiments, the solar absorptive heat transfer fluid can beautomotive automatic transmission fluid or propylene glycol, and thepigments or dyes can be conventional printing inks known in the art,carbon black, or other high absorbtivity substance, in powder form.

In some implementations, one or more of the surfaces of the base 102defining the insulation chamber 114 shown in FIGS. 16 and 17 can becoated with a low permeability coating. Further, in someimplementations, the insulation chamber 114 is in gas vapor flowcommunication with a low permeability bladder bag 103 external to thestructure or an expansion tank known in the art. By coating the base 102with a low permeability coating and using a low permeability bladder bag103 or expansion tank to supply and maintain gas in the insulationchamber 114, the rate at which gas permeates through the base 102 may besufficiently reduced to economically contain a noble or inert gas, suchas Argon or Nitrogen, within the insulation chamber.

In some embodiments, the solar energy collection system 10 can beoperated to reduce the overall temperature of the system in the eventthe temperature of the absorber exceeds a predetermined threshold. Asthe solar absorptive heat transfer fluid circulates through the system,the thermal storage mass 152 will increase in temperature if the currentenergy taken out of the system, either directly or through a thermalheat exchange element or heat exchanger (not shown) in energy transfercommunication with the thermal storage mass 152, is less than thecurrent sun input that is converted into heat.

More specifically, the temperature of the fluid exiting the thermalstorage mass 152 and entering the absorber 20 is approximately the sameas the temperature of the thermal storage mass. The temperature of thefluid flowing through the absorber 20 increases to a new temperaturegreater than the temperature of the thermal storage mass 152 as itabsorbs energy from the sun. The fluid exits the absorber at the newhigher temperature and comes into heat exchange contact with the thermalstorage mass, which causes the temperature of the thermal storage massto increase. If energy is not transferred from the system, the fluidexits the thermal storage mass at a temperature greater than when itexited the thermal mass in the previous cycle. In other words, thetemperatures of the components around the solar energy collection systemloop can increase in tandem. Without some mechanism to reduce the suninput converted to heat or increase the current energy consumption, thetemperature of one or more of the components around the loop may becomedangerously high and cause long-term damage to some or all of thecomponents including but not limited to any plastic, foam or fluidmaterials.

Based on the properties of the solar absorptive heat transfer fluid,plastic components and insulator components of the solar energyapparatus described herein, a predetermined maximum operatingtemperatures of the thermal storage mass T_(tm) _(—) _(max) and thecollection portion T_(c) _(—) _(max) may be selected where T_(c) _(—)_(max) is slightly above T_(tm) _(—) _(m). For example, in one specificimplementation, the thermal mass can be water, T_(tm) _(—) _(max) can beset to 180° F. (sufficiently below the boiling point of water), andT_(c) _(—) _(max) can be set to 195° F., which is somewhat below theboiling point of water or a composite liquid. The collector willcontinuously pump fluid through the absorber and transfer thermal energyto the thermal mass until the overall temperature T_(c) of thecollection portion reaches T_(c) _(—) _(max), at which time the pumpwill shut off and a fluid valve 113 located in the bottom header 60 andan air valve 115 located in the top header 62 will open. The fluid isthen allowed to drain out of the absorber 20 and into the fluidreservoir 154 via the fluid valve 113 and the line 162. As the fluiddrains, air entering through the air valve 115 replaces the fluid. Withno fluid being located within the absorber 20, the collector is placedin the non-operative state and solar energy penetrating the absorberwill be reflected by the reflective layer 44 shown in FIG. 1. Sincesolar energy is being reflected, rather than absorbed, the overalltemperature T_(c) of the collection portion will not exceed T_(c) _(—)_(max) and can be maintained below a safe operating limit.

In some embodiments, a control system, such as system 167, is included.The system 167 may include a microcomputer that monitors temperature atone or more locations within the solar energy collection system 10 andopens the valve described above when the temperature at the one or morelocations reaches a predetermined limit.

In some embodiments, the solar energy collection system can include anadditional safety mechanism to prevent overheating of the collectionsystem in the event the control system fails. The additional safetymechanism includes a snap switch, as commonly known in the art, whichforces the fluid to drain from the absorber if the control system failsto open the valve. For example, in some implementations, themicrocomputer of the control system can be programmed to open the valveat a T_(c) _(—) _(max) limit of 160° F. and the backup snap switch couldhave a temperature threshold of 160° F. If the microcomputer or itsinterfacing components fail, the snap switch will shut off at 160° F.,thus draining the fluid from the absorber. The use of a snap switch, orother similar device, provides a simple and reliable safety backup tothe control system.

After the fluid has drained from the absorber 20, the temperature of thecollection system will decrease. Once the temperature of the solarenergy collection system dips below a predetermined minimum temperature,the control system can close the fluid valve 113 and pump 150 can againcirculate solar absorptive heat transfer fluid through the absorber 20,which causes the air within the absorber exit the absorber through theair valve 115. Once the absorber 20 is full, the air valve 115 canclose.

In view of the many possible embodiments to which the principles of thedisclosed solar energy apparatus may be applied, it should be recognizedthat the illustrated embodiments are only examples and should not betaken as limiting the scope of the disclosure.

It can thus be seen that at least certain of solar energy absorptionapparatus embodiments set forth above can provide the followingadvantages among others:

-   1. Reduction in the cost of manufacturing due to, among other    things, the ability to make the apparatus with inexpensive materials    that, in some instances, can be extruded. For example, traditional    solar panels use an absorber made of metal and a top surface made of    a different material that allows light to pass through. Accordingly,    the absorber and top surface of traditional solar panels cannot be    extruded as one piece. In contrast, the use of solar absorptive heat    transfer fluid in the solar energy apparatus described herein allows    for the top layer and the absorber to be made of the same material.    Therefore, in some implementations, the top surface and the absorber    can formed as a single extruded part, which lowers manufacturing    cost.-   2. Reduction in the size, thickness, and weight due to, among other    things, a reduced volume and depth of absorptive fluid flowing    through the collection portion of the apparatus. For example, the    amount of solar absorptive heat transfer fluid to heat a typical    home may go from 100 gallons to 20 gallons, saving up to $20 per    month in operating costs over the life of the system.-   3. Reduced apparatus cost for each Joule (BTU) collected due to,    among other things, the reduced volume of absorptive fluid, the    unique composition of the absorptive fluid and plastic components.-   4. Prolonged operating life due to, among other things, a    construction made of plastic with particular optical and UV    characteristics and the use of reflective materials, layers, or    coatings for protecting underlying structures.-   5. Enhanced temperature control to prevent overheating and prolong    the life of the absorptive fluid and structural components of the    apparatus. For example, as one instance of overheating can cause    deleterious long-term effects on the components of an apparatus,    effectively eliminating such overheating by reflecting light back to    the sky promotes system reliability in a natural and reliable way.-   6. Potential for increased efficiency. The efficiency of the    collector is a direct function of the absorptivity of the solar    absorptive heat transfer fluid to visible and UV light. As such, as    better fluids become a reality, the efficiency of existing systems    can be increased by simply changing the fluid.-   7. Reduction in the cost of system and operation. By using less    solar absorptive heat transfer fluid, the cost of the system is    reduced. Additionally, the size, and thereby the cost, of the drain    back storage tank can be reduced, which results in less insulation    required to insulate the storage tank and a lower overall system    insulation cost.-   8. Uniform heat transfer to absorptive fluid. Since heat transport    is ubiquitous over the entire surface of the absorber, uniform heat    transfer is achieved at no additional cost. This ubiquity of heat    transfer completely obviates the economic trade-off between    conventional absorber thickness and riser pipe spacing.-   9. Quicker and easier installation compared to conventional solar    energy collectors.-   10. Increased efficiency due to, among other things, the ability to    construct vacuum insulation inexpensively to eliminate convective    and conductive heat losses from the absorber to the ambient air. In    some implementations, the vacuum insulation exists in panel form,    while in others the insulation exists within a cylinder.-   11. Reduced overheating, thereby allowing for use of inexpensive    materials and eliminating damage to circulation fluid.-   12. Increased efficiency due to shapes and configurations that    capture nearly 100% of the incident solar energy at any incident sun    angle.-   13. Increased efficiency due to utilization of infrared radiation    retention coatings.-   14. Increased safety due to control of the maximum operating    temperature of the device, thereby reducing effects of scalding and    eliminating steam.-   15. Increased design flexibility, as structural dimensions,    structural materials, fluid composition, maximum operating    temperature, stagnation temperature, environmental effects and    insulation properties remain controllable and predictable while    using common, low cost, materials and processes.-   16. Elimination of heat pipes and pipes that heat to a condenser    which has a glass-metal interface connecting to the top header. When    the header flow stops (stagnates), the glass-metal interface goes up    in temperature and can damage the evacuated tube since the tiniest    crack will let air in and ruin the vacuum. Coaxial solar absorptive    heat transfer fluid collectors eliminate this problem by having no    dissimilar materials that get hot and heat collection goes away    during stagnation because the black fluid drains out of the tubes.-   17. Increase in collection of more diffuse solar energy, possibly up    to 2 times more.-   18. Lower maintenance costs since components are limited to    temperatures that do not cause them long-term damage and cannot    cause heat transport fluid to become an agent of chemical attack    upon components that come in contact with the fluid.

1. A solar energy absorber, comprising: a front panel having a length, a width, a thickness, a first side edge and a second side edge opposite the first side edge; a rear panel having a length, a width, a thickness, a first side edge and a second side edge opposite the first side edge, wherein the rear panel is spaced apart a predetermined distance from and aligned parallel with the front panel; a first edge member coupling the front panel first side edge to the rear panel first side edge and extending the length of the front panel and rear panel; a second edge member coupling the front panel second side edge to the rear panel second side edge and extending the length of the front panel and rear panel; and at least one internal member located between the front panel and the rear panel, wherein there is at least one internal member has a height equal to the predetermined distance between the front panel and rear panel, is aligned perpendicular to the front panel and rear panel and parallel with the first edge member and second edge member and extends the length of front panel and rear panel to thereby form at least two fluid chambers within the solar energy absorber.
 2. A cylindrical solar energy absorber, comprising: a cylindrical inner conduit defining a fluid passageway having an inner diameter and an outer diameter; a cylindrical outer conduit coaxial with the inner conduit having an inner diameter and an outer diameter; and a spacer for maintaining a space between the inner conduit and the outer conduit, wherein the material of the inner conduit and outer conduit comprises transparent material and the space between the inner conduit and the outer conduit comprises a vacuum.
 3. A header for providing fluid communication between a series of solar energy absorbers, comprising: a fluid reservoir portion having an elongated tubular shape, an inside diameter and an outside diameter; and an absorber attachment portion having an elongated, geometrical shape; wherein the absorber attachment portion is aligned parallel to the fluid reservoir and is attached to the fluid reservoir; wherein a side of the absorber attachment portion extending away from the fluid reservoir includes an elongated slot extending partially into the absorber attachment portion for receiving the end of at least one absorber; and wherein a fluid inlet slot extends from the inside diameter of the fluid reservoir portion to the elongated slot extending partially into the absorber attachment portion.
 4. A solar energy panel, comprising: an absorber housing having a first open end and a second open end opposite the first open end, wherein the housing comprises: a top panel having a first surface and a second surface opposite the first surface; a bottom panel opposite the top panel, the bottom panel having a first surface and a second surface opposite the first surface; a left side panel; a right side panel opposite the left side panel; left side corner brackets, wherein the left side corner brackets couple the top panel to the left side panel and the bottom panel to the left side panel at a right angle such that the first surface of the top panel faces the second surface of the bottom surface; right side corner brackets, wherein the right side corner brackets couple the top panel to the right side panel and the bottom panel to the right side panel at a right angle such that the first surface of the top panel faces the second surface of the bottom surface; and at least one track formed on each of the first surface of the top panel and the second surface of the bottom panel, wherein the tracks are aligned parallel with the left and right panels and extend the length of the top and bottom panels; and an absorber assembly, wherein the absorber assembly comprises: an absorber having a first surface, a second surface opposite the first surface, a first end and a second end opposing the first end; a first header coupled to the first end of the absorber; a second header coupled to the second end; and at least one absorber flex beam coupled to each of the first surface and second surface of the absorber and extending away from the absorber and perpendicular to the absorber, wherein when the absorber is housed in the housing, the absorber flex beams are aligned with the tracks and are matingly received by the tracks to thereby position the absorber in the housing.
 5. A combined absorber and absorber housing assembly, comprising: a base having a top surface, a bottom surface opposite the top surface, an upper side surface, a lower side surface opposite the upper side surface; a left side surface and a right side surface opposite the left side surface; an upper wall coextensive with the upper side surface of the base and extending above the top surface of the base; a lower wall coextensive with the lower side surface of the base and extending above the top surface of the base; a left fluid chamber wall located on the top surface of the base, wherein the left fluid chamber wall is aligned with and extends the length of the left side surface and has a height smaller than the height the upper wall and lower wall extend above the top surface of the base; a right fluid chamber wall located on the top surface of the base, wherein the right fluid chamber wall is aligned with and extends the length of the right side surface and has a height smaller than the height the upper wall and lower wall extend above the top surface of the base; a left wall approximately equal in length and width to the left fluid chamber wall and located on top of the left fluid chamber wall, wherein the height of the left wall and left fluid chamber wall combined is approximately equal to the height the upper wall and lower wall each extend above the top surface of the base; a right wall approximately equal in length and width to the right fluid chamber wall and located on top of the right fluid chamber wall, wherein the height of the right wall and the right fluid chamber wall is approximately equal to the height the upper wall and lower wall each extend above the top surface of the base; at least one fluid chamber rib located on the top surface of the base between the right fluid chamber wall and the left fluid chamber wall and aligned in parallel with the left fluid chamber wall and the right fluid chamber wall, wherein the height of the at least one fluid chamber rib is approximately equal to the height of the right fluid chamber wall and the left fluid chamber wall; an inner optical layer formed on the at least one fluid chamber rib, the right fluid chamber wall and the left fluid chamber wall and extending to the upper wall and the lower wall to thereby encapsulate the area under the inner optical layer and form fluid chambers; at least one insulation chamber rib formed on the inner optical layer, wherein the combined height of the at least one fluid chamber rib, the inner optical layer and at the least one insulation chamber rib is approximately equal to the height the upper wall and lower wall each extend above the top surface of the base; and an outer optical layer formed on the at least one insulation chamber rib, the upper wall, the lower wall, the left wall and the right wall to thereby encapsulate the area under the outer optical layer and form insulation chambers. 